Help with a switching power supply.

Discussion in 'The Projects Forum' started by Mellontikos, Apr 15, 2015.

  1. Mellontikos

    Thread Starter New Member

    Apr 15, 2015
    Hello everyone.

    New guy here. I'm mostly an IT guy, but I do electronics as a hobby. With that said, I'm am by no means an expert on electronics, but do understand the basics.

    Anyway, I have a line mixer here (sound mixing) called the Soundcraft EFX8. The mixer just decided to not power on at all a couple of weeks ago.

    So I tested the fuse of course, and it was fine. So I took out the power supply and tested everything I could (diodes, resistors, chokes, mosfets, etc).

    There's some parts I am unsure how to test, for example, there's a IC on board that I have no clue how to test, and the main transformer (which I am assuming is a step down transformer) which I have no idea how to test either.

    I see two MOSFET's in there, one is in the high voltage side of the circuit, and the other is in the low voltage side.

    I tested both onboard (with the voltmeter set on continuity, measuring the source/drain, touching the gate, then measuring again the source/drain). I believed that this was the part that was defective. So I bought a new MOSFET and just replaced it.

    Sadly, no luck. Mixer is still DOA :(

    I'm not sure how else to test this device at this point.

    If someone here is familiar with switching power supplies (or even better if you have experience repairing musical equipment) I wouldn't mind a hand.

    I can provide pics of everything if it help.
  2. izon


    Mar 17, 2013
    Check out . They have a tech support number. Also Google shows a few sites when you use "Soundcraft EFX8 service manual" in a search that provide a free download giving a manual with full schematics.
    Hope this helps.
  3. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    How do you know that the power supply is bad? Did you measure its outputs?
    Photos - YES.

  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    you cant test components in circuit,sounds like its a switched mode psu, can you post pictures of it...